[v7,04/15] PM / EM: add support for other devices than CPUs in Energy Model
diff mbox series

Message ID 20200511111912.3001-5-lukasz.luba@arm.com
State New
Headers show
Series
  • Add support for devices in the Energy Model
Related show

Commit Message

Lukasz Luba May 11, 2020, 11:19 a.m. UTC
Add support for other devices that CPUs. The registration function
does not require a valid cpumask pointer and is ready to handle new
devices. Some of the internal structures has been reorganized in order to
keep consistent view (like removing per_cpu pd pointers). To track usage
of the Energy Model structures, they are protected with kref.

Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
---
 include/linux/device.h       |   5 +
 include/linux/energy_model.h |  28 +++--
 kernel/power/energy_model.c  | 237 ++++++++++++++++++++++++-----------
 3 files changed, 187 insertions(+), 83 deletions(-)

Comments

Quentin Perret May 11, 2020, 1:43 p.m. UTC | #1
Hey Lukasz,

On Monday 11 May 2020 at 12:19:01 (+0100), Lukasz Luba wrote:
<snip>
> @@ -27,12 +29,15 @@ struct em_perf_state {
>   * em_perf_domain - Performance domain
>   * @table:		List of performance states, in ascending order
>   * @nr_perf_states:	Number of performance states
> - * @cpus:		Cpumask covering the CPUs of the domain
> + * @cpus:		Cpumask covering the CPUs of the domain. It's here
> + *			for performance reasons to avoid potential cache
> + *			misses during energy calculations in the scheduler

And because that saves a pointer, and simplifies allocating/freeing that
memory region :)

<snip>
> diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
> index 5b8a1566526a..9cc7f2973600 100644
> --- a/kernel/power/energy_model.c
> +++ b/kernel/power/energy_model.c
> @@ -2,8 +2,9 @@
>  /*
>   * Energy Model of CPUs

Should this comment change too?

<snip>
> -static void em_debug_create_pd(struct em_perf_domain *pd, int cpu)
> +static void em_debug_create_pd(struct device *dev)
>  {
>  	struct dentry *d;
> -	char name[8];
>  	int i;
>  
> -	snprintf(name, sizeof(name), "pd%d", cpu);
> -
>  	/* Create the directory of the performance domain */
> -	d = debugfs_create_dir(name, rootdir);
> +	d = debugfs_create_dir(dev_name(dev), rootdir);

So what will be the name for the perf domain of CPUs now? cpuX?

<snip>
> @@ -142,8 +149,8 @@ em_create_pd(struct device *dev, int nr_states, struct em_data_callback *cb,
>  		 */
>  		opp_eff = freq / power;
>  		if (opp_eff >= prev_opp_eff)
> -			pr_warn("pd%d: hertz/watts ratio non-monotonically decreasing: em_perf_state %d >= em_perf_state%d\n",
> -					cpu, i, i - 1);
> +			dev_dbg(dev, "EM: hertz/watts ratio non-monotonically decreasing: em_perf_state %d >= em_perf_state%d\n",
> +					i, i - 1);

It feels like changing from warn to debug doesn't really belong to this
patch no?

<snip>
> @@ -216,47 +274,50 @@ int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
>  	 */
>  	mutex_lock(&em_pd_mutex);
>  
> -	for_each_cpu(cpu, span) {
> -		/* Make sure we don't register again an existing domain. */
> -		if (READ_ONCE(per_cpu(em_data, cpu))) {
> -			ret = -EEXIST;
> -			goto unlock;
> -		}
> +	if (dev->em_pd) {
> +		ret = -EEXIST;
> +		goto unlock;
> +	}
>  
> -		/*
> -		 * All CPUs of a domain must have the same micro-architecture
> -		 * since they all share the same table.
> -		 */
> -		cap = arch_scale_cpu_capacity(cpu);
> -		if (prev_cap && prev_cap != cap) {
> -			pr_err("CPUs of %*pbl must have the same capacity\n",
> -							cpumask_pr_args(span));
> +	if (_is_cpu_device(dev)) {

Something like

	if (!_is_cpu_device(dev))
		goto device;

would limit the diff a bit, but that may just be personal taste.

But appart from these nits, the patch LGTM.

Thanks,
Quentin
Lukasz Luba May 12, 2020, 11:38 a.m. UTC | #2
On 5/11/20 2:43 PM, Quentin Perret wrote:
> Hey Lukasz,
> 
> On Monday 11 May 2020 at 12:19:01 (+0100), Lukasz Luba wrote:
> <snip>
>> @@ -27,12 +29,15 @@ struct em_perf_state {
>>    * em_perf_domain - Performance domain
>>    * @table:		List of performance states, in ascending order
>>    * @nr_perf_states:	Number of performance states
>> - * @cpus:		Cpumask covering the CPUs of the domain
>> + * @cpus:		Cpumask covering the CPUs of the domain. It's here
>> + *			for performance reasons to avoid potential cache
>> + *			misses during energy calculations in the scheduler
> 
> And because that saves a pointer, and simplifies allocating/freeing that
> memory region :)

True, I will add this also:
'and simplifies allocating/freeing that memory region'

> 
> <snip>
>> diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
>> index 5b8a1566526a..9cc7f2973600 100644
>> --- a/kernel/power/energy_model.c
>> +++ b/kernel/power/energy_model.c
>> @@ -2,8 +2,9 @@
>>   /*
>>    * Energy Model of CPUs
> 
> Should this comment change too?

Yes, indeed. I will adjust it.

> 
> <snip>
>> -static void em_debug_create_pd(struct em_perf_domain *pd, int cpu)
>> +static void em_debug_create_pd(struct device *dev)
>>   {
>>   	struct dentry *d;
>> -	char name[8];
>>   	int i;
>>   
>> -	snprintf(name, sizeof(name), "pd%d", cpu);
>> -
>>   	/* Create the directory of the performance domain */
>> -	d = debugfs_create_dir(name, rootdir);
>> +	d = debugfs_create_dir(dev_name(dev), rootdir);
> 
> So what will be the name for the perf domain of CPUs now? cpuX?

yeap, it will be 'cpu0', 'cpu4', etc...

> 
> <snip>
>> @@ -142,8 +149,8 @@ em_create_pd(struct device *dev, int nr_states, struct em_data_callback *cb,
>>   		 */
>>   		opp_eff = freq / power;
>>   		if (opp_eff >= prev_opp_eff)
>> -			pr_warn("pd%d: hertz/watts ratio non-monotonically decreasing: em_perf_state %d >= em_perf_state%d\n",
>> -					cpu, i, i - 1);
>> +			dev_dbg(dev, "EM: hertz/watts ratio non-monotonically decreasing: em_perf_state %d >= em_perf_state%d\n",
>> +					i, i - 1);
> 
> It feels like changing from warn to debug doesn't really belong to this
> patch no?

I thought that these prints are not worth to introduce another patch.
This warning is a bit tricky, because we (SW eng) basically are not able
to tweak OPPs, we can only remove them to calm down this warning.

There are platforms, with dozen of OPPs, seeing this. Warnings triggers 
the automated tests scripts, which are sensitive to dmesg log level and
cause developers to spent time and investigate the issue.

Then, what if these OPPs are needed because the thermal was tested OK
with some OPPs which unfortunately are triggering also this warning.
They cannot remove these OPPS, but the warning would stay. We might see
this also for GPUs.

I decided to change it into dbg, due to the reason above.

> 
> <snip>
>> @@ -216,47 +274,50 @@ int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
>>   	 */
>>   	mutex_lock(&em_pd_mutex);
>>   
>> -	for_each_cpu(cpu, span) {
>> -		/* Make sure we don't register again an existing domain. */
>> -		if (READ_ONCE(per_cpu(em_data, cpu))) {
>> -			ret = -EEXIST;
>> -			goto unlock;
>> -		}
>> +	if (dev->em_pd) {
>> +		ret = -EEXIST;
>> +		goto unlock;
>> +	}
>>   
>> -		/*
>> -		 * All CPUs of a domain must have the same micro-architecture
>> -		 * since they all share the same table.
>> -		 */
>> -		cap = arch_scale_cpu_capacity(cpu);
>> -		if (prev_cap && prev_cap != cap) {
>> -			pr_err("CPUs of %*pbl must have the same capacity\n",
>> -							cpumask_pr_args(span));
>> +	if (_is_cpu_device(dev)) {
> 
> Something like
> 
> 	if (!_is_cpu_device(dev))
> 		goto device;
> 
> would limit the diff a bit, but that may just be personal taste.

Possible

> 
> But appart from these nits, the patch LGTM.

Thank you for the review.

I will wait for Daniel's (because he suggested the em_pd inside
device struct) comments and if there is no other issues I will just
resend the patch with adjusted comment fields in response.

Regards,
Lukasz

> 
> Thanks,
> Quentin
>

Patch
diff mbox series

diff --git a/include/linux/device.h b/include/linux/device.h
index ac8e37cd716a..7023d3ea189b 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -13,6 +13,7 @@ 
 #define _DEVICE_H_
 
 #include <linux/dev_printk.h>
+#include <linux/energy_model.h>
 #include <linux/ioport.h>
 #include <linux/kobject.h>
 #include <linux/klist.h>
@@ -559,6 +560,10 @@  struct device {
 	struct dev_pm_info	power;
 	struct dev_pm_domain	*pm_domain;
 
+#ifdef CONFIG_ENERGY_MODEL
+	struct em_perf_domain	*em_pd;
+#endif
+
 #ifdef CONFIG_GENERIC_MSI_IRQ_DOMAIN
 	struct irq_domain	*msi_domain;
 #endif
diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
index 7076cb22b247..f5a88486d1c4 100644
--- a/include/linux/energy_model.h
+++ b/include/linux/energy_model.h
@@ -12,8 +12,10 @@ 
 
 /**
  * em_perf_state - Performance state of a performance domain
- * @frequency:	The CPU frequency in KHz, for consistency with CPUFreq
- * @power:	The power consumed by 1 CPU at this level, in milli-watts
+ * @frequency:	The frequency in KHz, for consistency with CPUFreq
+ * @power:	The power consumed at this level, in milli-watts (by 1 CPU or
+		by a registered device). It can be a total power: static and
+		dynamic.
  * @cost:	The cost coefficient associated with this level, used during
  *		energy calculation. Equal to: power * max_frequency / frequency
  */
@@ -27,12 +29,15 @@  struct em_perf_state {
  * em_perf_domain - Performance domain
  * @table:		List of performance states, in ascending order
  * @nr_perf_states:	Number of performance states
- * @cpus:		Cpumask covering the CPUs of the domain
+ * @cpus:		Cpumask covering the CPUs of the domain. It's here
+ *			for performance reasons to avoid potential cache
+ *			misses during energy calculations in the scheduler
  *
- * A "performance domain" represents a group of CPUs whose performance is
- * scaled together. All CPUs of a performance domain must have the same
- * micro-architecture. Performance domains often have a 1-to-1 mapping with
- * CPUFreq policies.
+ * In case of CPU device, a "performance domain" represents a group of CPUs
+ * whose performance is scaled together. All CPUs of a performance domain
+ * must have the same micro-architecture. Performance domains often have
+ * a 1-to-1 mapping with CPUFreq policies. In case of other devices the 'cpus'
+ * field is unused.
  */
 struct em_perf_domain {
 	struct em_perf_state *table;
@@ -71,10 +76,12 @@  struct em_data_callback {
 #define EM_DATA_CB(_active_power_cb) { .active_power = &_active_power_cb }
 
 struct em_perf_domain *em_cpu_get(int cpu);
+struct em_perf_domain *em_pd_get(struct device *dev);
 int em_register_perf_domain(cpumask_t *span, unsigned int nr_states,
 						struct em_data_callback *cb);
 int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
 				struct em_data_callback *cb, cpumask_t *span);
+void em_dev_unregister_perf_domain(struct device *dev);
 
 /**
  * em_pd_energy() - Estimates the energy consumed by the CPUs of a perf. domain
@@ -184,10 +191,17 @@  int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
 {
 	return -EINVAL;
 }
+static inline void em_dev_unregister_perf_domain(struct device *dev)
+{
+}
 static inline struct em_perf_domain *em_cpu_get(int cpu)
 {
 	return NULL;
 }
+static inline struct em_perf_domain *em_pd_get(struct device *dev)
+{
+	return NULL;
+}
 static inline unsigned long em_pd_energy(struct em_perf_domain *pd,
 			unsigned long max_util, unsigned long sum_util)
 {
diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
index 5b8a1566526a..9cc7f2973600 100644
--- a/kernel/power/energy_model.c
+++ b/kernel/power/energy_model.c
@@ -2,8 +2,9 @@ 
 /*
  * Energy Model of CPUs
  *
- * Copyright (c) 2018, Arm ltd.
+ * Copyright (c) 2018-2020, Arm ltd.
  * Written by: Quentin Perret, Arm ltd.
+ * Improvements provided by: Lukasz Luba, Arm ltd.
  */
 
 #define pr_fmt(fmt) "energy_model: " fmt
@@ -15,15 +16,17 @@ 
 #include <linux/sched/topology.h>
 #include <linux/slab.h>
 
-/* Mapping of each CPU to the performance domain to which it belongs. */
-static DEFINE_PER_CPU(struct em_perf_domain *, em_data);
-
 /*
  * Mutex serializing the registrations of performance domains and letting
  * callbacks defined by drivers sleep.
  */
 static DEFINE_MUTEX(em_pd_mutex);
 
+static bool _is_cpu_device(struct device *dev)
+{
+	return (dev->bus == &cpu_subsys);
+}
+
 #ifdef CONFIG_DEBUG_FS
 static struct dentry *rootdir;
 
@@ -49,22 +52,30 @@  static int em_debug_cpus_show(struct seq_file *s, void *unused)
 }
 DEFINE_SHOW_ATTRIBUTE(em_debug_cpus);
 
-static void em_debug_create_pd(struct em_perf_domain *pd, int cpu)
+static void em_debug_create_pd(struct device *dev)
 {
 	struct dentry *d;
-	char name[8];
 	int i;
 
-	snprintf(name, sizeof(name), "pd%d", cpu);
-
 	/* Create the directory of the performance domain */
-	d = debugfs_create_dir(name, rootdir);
+	d = debugfs_create_dir(dev_name(dev), rootdir);
 
-	debugfs_create_file("cpus", 0444, d, pd->cpus, &em_debug_cpus_fops);
+	if (_is_cpu_device(dev))
+		debugfs_create_file("cpus", 0444, d, dev->em_pd->cpus,
+				    &em_debug_cpus_fops);
 
 	/* Create a sub-directory for each performance state */
-	for (i = 0; i < pd->nr_perf_states; i++)
-		em_debug_create_ps(&pd->table[i], d);
+	for (i = 0; i < dev->em_pd->nr_perf_states; i++)
+		em_debug_create_ps(&dev->em_pd->table[i], d);
+
+}
+
+static void em_debug_remove_pd(struct device *dev)
+{
+	struct dentry *debug_dir;
+
+	debug_dir = debugfs_lookup(dev_name(dev), rootdir);
+	debugfs_remove_recursive(debug_dir);
 }
 
 static int __init em_debug_init(void)
@@ -76,40 +87,34 @@  static int __init em_debug_init(void)
 }
 core_initcall(em_debug_init);
 #else /* CONFIG_DEBUG_FS */
-static void em_debug_create_pd(struct em_perf_domain *pd, int cpu) {}
+static void em_debug_create_pd(struct device *dev) {}
+static void em_debug_remove_pd(struct device *dev) {}
 #endif
-static struct em_perf_domain *
-em_create_pd(struct device *dev, int nr_states, struct em_data_callback *cb,
-	     cpumask_t *span)
+
+static int em_create_perf_table(struct device *dev, struct em_perf_domain *pd,
+				int nr_states, struct em_data_callback *cb)
 {
 	unsigned long opp_eff, prev_opp_eff = ULONG_MAX;
 	unsigned long power, freq, prev_freq = 0;
-	int i, ret, cpu = cpumask_first(span);
 	struct em_perf_state *table;
-	struct em_perf_domain *pd;
+	int i, ret;
 	u64 fmax;
 
-	if (!cb->active_power)
-		return NULL;
-
-	pd = kzalloc(sizeof(*pd) + cpumask_size(), GFP_KERNEL);
-	if (!pd)
-		return NULL;
-
 	table = kcalloc(nr_states, sizeof(*table), GFP_KERNEL);
 	if (!table)
-		goto free_pd;
+		return -ENOMEM;
 
 	/* Build the list of performance states for this performance domain */
 	for (i = 0, freq = 0; i < nr_states; i++, freq++) {
 		/*
 		 * active_power() is a driver callback which ceils 'freq' to
-		 * lowest performance state of 'cpu' above 'freq' and updates
+		 * lowest performance state of 'dev' above 'freq' and updates
 		 * 'power' and 'freq' accordingly.
 		 */
 		ret = cb->active_power(&power, &freq, dev);
 		if (ret) {
-			pr_err("pd%d: invalid perf. state: %d\n", cpu, ret);
+			dev_err(dev, "EM: invalid perf. state: %d\n",
+				ret);
 			goto free_ps_table;
 		}
 
@@ -118,7 +123,8 @@  em_create_pd(struct device *dev, int nr_states, struct em_data_callback *cb,
 		 * higher performance states.
 		 */
 		if (freq <= prev_freq) {
-			pr_err("pd%d: non-increasing freq: %lu\n", cpu, freq);
+			dev_err(dev, "EM: non-increasing freq: %lu\n",
+				freq);
 			goto free_ps_table;
 		}
 
@@ -127,7 +133,8 @@  em_create_pd(struct device *dev, int nr_states, struct em_data_callback *cb,
 		 * positive, in milli-watts and to fit into 16 bits.
 		 */
 		if (!power || power > EM_MAX_POWER) {
-			pr_err("pd%d: invalid power: %lu\n", cpu, power);
+			dev_err(dev, "EM: invalid power: %lu\n",
+				power);
 			goto free_ps_table;
 		}
 
@@ -142,8 +149,8 @@  em_create_pd(struct device *dev, int nr_states, struct em_data_callback *cb,
 		 */
 		opp_eff = freq / power;
 		if (opp_eff >= prev_opp_eff)
-			pr_warn("pd%d: hertz/watts ratio non-monotonically decreasing: em_perf_state %d >= em_perf_state%d\n",
-					cpu, i, i - 1);
+			dev_dbg(dev, "EM: hertz/watts ratio non-monotonically decreasing: em_perf_state %d >= em_perf_state%d\n",
+					i, i - 1);
 		prev_opp_eff = opp_eff;
 	}
 
@@ -156,30 +163,82 @@  em_create_pd(struct device *dev, int nr_states, struct em_data_callback *cb,
 
 	pd->table = table;
 	pd->nr_perf_states = nr_states;
-	cpumask_copy(to_cpumask(pd->cpus), span);
-
-	em_debug_create_pd(pd, cpu);
 
-	return pd;
+	return 0;
 
 free_ps_table:
 	kfree(table);
-free_pd:
-	kfree(pd);
+	return -EINVAL;
+}
+
+static int em_create_pd(struct device *dev, int nr_states,
+			struct em_data_callback *cb, cpumask_t *cpus)
+{
+	struct em_perf_domain *pd;
+	struct device *cpu_dev;
+	int cpu, ret;
+
+	if (_is_cpu_device(dev)) {
+		pd = kzalloc(sizeof(*pd) + cpumask_size(), GFP_KERNEL);
+		if (!pd)
+			return -ENOMEM;
+
+		cpumask_copy(em_span_cpus(pd), cpus);
+	} else {
+		pd = kzalloc(sizeof(*pd), GFP_KERNEL);
+		if (!pd)
+			return -ENOMEM;
+	}
+
+	ret = em_create_perf_table(dev, pd, nr_states, cb);
+	if (ret) {
+		kfree(pd);
+		return ret;
+	}
 
-	return NULL;
+	if (_is_cpu_device(dev))
+		for_each_cpu(cpu, cpus) {
+			cpu_dev = get_cpu_device(cpu);
+			cpu_dev->em_pd = pd;
+		}
+	else
+		dev->em_pd = pd;
+
+	return 0;
 }
 
+/**
+ * em_pd_get() - Return the performance domain for a device
+ * @dev : Device to find the performance domain for
+ *
+ * Returns the performance domain to which 'dev' belongs, or NULL if it doesn't
+ * exist.
+ */
+struct em_perf_domain *em_pd_get(struct device *dev)
+{
+	if (IS_ERR_OR_NULL(dev))
+		return NULL;
+
+	return dev->em_pd;
+}
+EXPORT_SYMBOL_GPL(em_pd_get);
+
 /**
  * em_cpu_get() - Return the performance domain for a CPU
  * @cpu : CPU to find the performance domain for
  *
- * Return: the performance domain to which 'cpu' belongs, or NULL if it doesn't
+ * Returns the performance domain to which 'cpu' belongs, or NULL if it doesn't
  * exist.
  */
 struct em_perf_domain *em_cpu_get(int cpu)
 {
-	return READ_ONCE(per_cpu(em_data, cpu));
+	struct device *cpu_dev;
+
+	cpu_dev = get_cpu_device(cpu);
+	if (!cpu_dev)
+		return NULL;
+
+	return em_pd_get(cpu_dev);
 }
 EXPORT_SYMBOL_GPL(em_cpu_get);
 
@@ -188,7 +247,7 @@  EXPORT_SYMBOL_GPL(em_cpu_get);
  * @dev		: Device for which the EM is to register
  * @nr_states	: Number of performance states to register
  * @cb		: Callback functions providing the data of the Energy Model
- * @span	: Pointer to cpumask_t, which in case of a CPU device is
+ * @cpus	: Pointer to cpumask_t, which in case of a CPU device is
  *		obligatory. It can be taken from i.e. 'policy->cpus'. For other
  *		type of devices this should be set to NULL.
  *
@@ -201,13 +260,12 @@  EXPORT_SYMBOL_GPL(em_cpu_get);
  * Return 0 on success
  */
 int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
-				struct em_data_callback *cb, cpumask_t *span)
+				struct em_data_callback *cb, cpumask_t *cpus)
 {
 	unsigned long cap, prev_cap = 0;
-	struct em_perf_domain *pd;
-	int cpu, ret = 0;
+	int cpu, ret;
 
-	if (!dev || !span || !nr_states || !cb)
+	if (!dev || !nr_states || !cb)
 		return -EINVAL;
 
 	/*
@@ -216,47 +274,50 @@  int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
 	 */
 	mutex_lock(&em_pd_mutex);
 
-	for_each_cpu(cpu, span) {
-		/* Make sure we don't register again an existing domain. */
-		if (READ_ONCE(per_cpu(em_data, cpu))) {
-			ret = -EEXIST;
-			goto unlock;
-		}
+	if (dev->em_pd) {
+		ret = -EEXIST;
+		goto unlock;
+	}
 
-		/*
-		 * All CPUs of a domain must have the same micro-architecture
-		 * since they all share the same table.
-		 */
-		cap = arch_scale_cpu_capacity(cpu);
-		if (prev_cap && prev_cap != cap) {
-			pr_err("CPUs of %*pbl must have the same capacity\n",
-							cpumask_pr_args(span));
+	if (_is_cpu_device(dev)) {
+		if (!cpus) {
+			dev_err(dev, "EM: invalid CPU mask\n");
 			ret = -EINVAL;
 			goto unlock;
 		}
-		prev_cap = cap;
+
+		for_each_cpu(cpu, cpus) {
+			if (em_cpu_get(cpu)) {
+				dev_err(dev, "EM: exists for CPU%d\n", cpu);
+				ret = -EEXIST;
+				goto unlock;
+			}
+			/*
+			 * All CPUs of a domain must have the same
+			 * micro-architecture since they all share the same
+			 * table.
+			 */
+			cap = arch_scale_cpu_capacity(cpu);
+			if (prev_cap && prev_cap != cap) {
+				dev_err(dev, "EM: CPUs of %*pbl must have the same capacity\n",
+					cpumask_pr_args(cpus));
+
+				ret = -EINVAL;
+				goto unlock;
+			}
+			prev_cap = cap;
+		}
 	}
 
-	/* Create the performance domain and add it to the Energy Model. */
-	pd = em_create_pd(dev, nr_states, cb, span);
-	if (!pd) {
-		ret = -EINVAL;
+	ret = em_create_pd(dev, nr_states, cb, cpus);
+	if (ret)
 		goto unlock;
-	}
 
-	for_each_cpu(cpu, span) {
-		/*
-		 * The per-cpu array can be read concurrently from em_cpu_get().
-		 * The barrier enforces the ordering needed to make sure readers
-		 * can only access well formed em_perf_domain structs.
-		 */
-		smp_store_release(per_cpu_ptr(&em_data, cpu), pd);
-	}
+	em_debug_create_pd(dev);
+	dev_info(dev, "EM: created perf domain\n");
 
-	pr_debug("Created perf domain %*pbl\n", cpumask_pr_args(span));
 unlock:
 	mutex_unlock(&em_pd_mutex);
-
 	return ret;
 }
 EXPORT_SYMBOL_GPL(em_dev_register_perf_domain);
@@ -285,3 +346,27 @@  int em_register_perf_domain(cpumask_t *span, unsigned int nr_states,
 	return em_dev_register_perf_domain(cpu_dev, nr_states, cb, span);
 }
 EXPORT_SYMBOL_GPL(em_register_perf_domain);
+
+/**
+ * em_dev_unregister_perf_domain() - Unregister Energy Model (EM) for a device
+ * @dev		: Device for which the EM is registered
+ *
+ * Try to unregister the EM for the specified device (but not a CPU).
+ */
+void em_dev_unregister_perf_domain(struct device *dev)
+{
+	if (IS_ERR_OR_NULL(dev) || !dev->em_pd)
+		return;
+
+	if (_is_cpu_device(dev))
+		return;
+
+	mutex_lock(&em_pd_mutex);
+	em_debug_remove_pd(dev);
+
+	kfree(dev->em_pd->table);
+	kfree(dev->em_pd);
+	dev->em_pd = NULL;
+	mutex_unlock(&em_pd_mutex);
+}
+EXPORT_SYMBOL_GPL(em_dev_unregister_perf_domain);